Chemiluminescent determination of L-cysteine with the lucigenin-carbon dot system

This work describes a new chemiluminescence (CL) system that is composed of lucigenin and carbon dots (CDs). The CDs display absorption peak at 260 nm and fluorescence with a emission peak centered at 524 nm (photo-excited at 470 nm). They were synthesized by hydrothermal treatment of starch and characterized by Fourier transform infrared spectroscopy, high resolution transmission electron microscopy, UV-vis absorption spectra and fluorescence spectra. The effects of oxygen and free radical scavengers on the CL system and on the CL spectra were investigated to elucidate the CL mechanism. It is found that L-cysteine (Cys) enhances the blue CL of the lucigenin-CD system by 59%. The finding was used to design a method for the determination of Cys. CL increases linearly in the 10.0 to 100 mu M Cys concentration range, and the detection limit is 8.8 mu M (at an S/N ratio of 3). The assay is highly selective over other amino acids. Conceivably, this novel CL system paves the way to numerous new assays based on the use of lucigenin.